Gray”s anatomy review pdf download

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A photograph of hairs on a human arm, with each hair based in a hair follicle. The thicker the hair, the more the number of sebaceous gray’s anatomy review pdf download there are.

The average growth rate of healthy hair follicles on the scalp is nearly 0. Cell division in the papilla is either rare or non-existent. The bulge is in the outer root sheath at the insertion point of the arrector pili muscle. It houses several types of stem cells, which supply the entire hair follicle with new cells, and take part in healing the epidermis after a wound. Hair follicle nerve receptors sense the position of the hairs.

Before a baby is born, the epithelium and underlying mesenchyma interact to form hair follicles. Each phase has several morphologically and histologically distinguishable sub-phases. The cycle’s length varies on different parts of the body. Growth cycles are controlled by a chemical signal like epidermal growth factor. Anagen is the color phase of hair follicles. The color of your hair will start to fade because the cell only last a couple months.

The catagen phase is a short transition stage that occurs at the end of the anagen phase. It signals the end of the active growth of a hair. 3 weeks while a club hair is formed. The telogen phase is the resting phase of the hair follicle. The club hair is the final product of a hair follicle in the telogen stage, and is a dead, fully keratinized hair. Fifty to one-hundred club hairs are shed daily from a normal scalp. Scalp: The time these phases last varies from person to person.